This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-070811, filed Mar. 13, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a print apparatus such as a printer, and the like, and more particularly, to a printer such as an inkjet printer, and the like arranged such that inkjet heads are mounted on a carriage and power is supplied from a printer main body side to the carriage through cables.
2. Description of the Related Art
Conventionally, it is sometimes a case that inkjet printers have a plurality of print heads mounted thereon to eject inks having a different color for the purpose of making multi-color print, and so on.
In this case, a power supply having a sufficient electric power is disposed to the printer main body side to perform recording by driving the plurality of print heads at the same time. The plurality of print heads are connected to the printer main body side through many power supply lines and control signal lines.
An example of an arrangement of an inkjet printer according the conventional art will be described here with reference to FIG. 1 showing the example. FIG. 1 shows the arrangement of the inkjet printer which performes recording by driving a plurality of print heads 111-1 to 111-6 at the same time. That is, a main power supply 104 is mounted on a printer main body 101 side. The main power supply 104 is connected to a plurality of voltage converters 109-1 to 109-6.
The outputs of the voltage converters 109-1 to 109-6 are connected to the inputs of head drive units 110-1 to 110-6, respectively. Further, a CPU 105 is mounted on the main body 101 to control the inkjet printer in its entirety. The control signal lines of the CPU 105 are connected to a head voltage controller 108, an image data processing unit 106, and a head drive controller 107, respectively. The printer main body 101 arranged as described above is connected to a carriage 103 side through a cable 102 so as to freely communicate therewith.
The plurality of print heads 111-1 to 111-6 are mounted on the carriage 103. The power supply lines and control signal lines are connected to the print heads 111-1 to 111-6, respectively. Further, the outputs from temperature detectors (not shown) included in the print heads 111-1 to 111-6 are fed back to the CPU 105 on the printer main body 101 side (hereinafter, this arrangement is referred to as prior art 1).
Nowadays, there have been also developed printers having a head voltage generation circuit disposed in each of print heads to generate a drive voltage for driving each print head. It is also contemplated to dispose the head voltage generation circuits the print heads, as described above (hereinafter, this arrangement is referred to as prior art 2).
Jpn. Pat. Appln. KOKAI Publication No. 7-25038, for example, discloses a technology of an inkjet recording apparatus that is roughly divided into a recording device section (mainly composed of print heads, and a carriage on which the print heads are mounted) and a machine main body (mainly composed of a power supply, respective control circuits, and respective head drive circuits) in which the drive of the recording apparatus section is controlled from the machine main body side. In this technology, the print heads are driven and controlled by electrically connecting the machine main body side to the recording device section through cables so as not to interfere with the movement of the carriage.
In this technology, a cable for connecting the machine main body side to the carriage side contains a control signal line and a power supply line for one set of the print heads, and it further contains a print head selection signal line. Therefore the number of control signal lines and voltage supply lines is reduced. That is, machine main body select one of the plurality of recording heads which is used for recording by using the the print head selection line, and a control signal and a drive voltage are supplied only to the selected print head (hereinafter, this arrangement is referred to as prior art 3).
Jpn. Pat. Appln. KOKAI Publication No. 2000-203014 discloses a technology of an inkjet printer having a head, a carriage, and a head drive circuit, wherein the head drive circuit has a plurality of selection units, which are connected to respective piezo electric elements and can receive drive signals, a controller which controls the selection units, and a plurality of voltage/current amplifiers which amplify the drive signals that are supplied to the piezo electric elements (hereinafter, this arrangement is referred to as prior art 4).
However, the prior art 1 has a problem in that while it is provided with the plurality of print heads to realize multi-gradation recording, when the print heads are driven at the same time, the number of the control signal lines and the power supply lines of the cable 102 increases as the number of the print heads 111-1 to 111-6 increases.
That is, since the print heads 111-1 to 111-6 must be individually controlled, it is necessary to provide the control signal lines according to the number of the print heads, which results in an increase in the number of the control signal lines. Further, when a different drive voltage is supplied to each drive head, the power supply lines must be provided according to the number of the print heads, which results in an increase in the number of the power supply lines.
Further, while the length of the cable 102 is determined according to the moving range of the carriage 103, the length thereof must be increased in a printer which prints a larger image because the carriage 103 moves in a wider range. In this case, a predetermined drive voltage cannot be supplied to the print heads 111-1 to 111-6 because the drive voltage generated on the printer main body 101 side is dropped by the resistance component and the inductance component of the cable 102 itself before it is supplied to the print heads 111-1 to 111-6 through the cable 102.
To solve this problem, it is contemplated to generate the drive voltage on the machine main body side at a higher level in consideration of the drop thereof.
However, this is against a today""s requirement for reducing power consumption.
Further, when it is desired to abruptly apply a large drive voltage is to the print heads, the long cable interfere contribute to make the rise time of the drive voltage longer. Accordingly, there is a possibility that the print heads cannot be driven at predetermined timing.
In the arrangement of the prior art 2, the temperature of the print heads themselves is excessively increased by the heat generated by the head voltage generating circuits disposed in the print heads. Thus, there is a possibility that ink ejection characteristics are made abnormal when inks are ejected and the quality of a recorded image is deteriorated thereby.
Further, each print head is not designed specifically for a particular ink but has versatility such that it can cope with a plurality of ink colors. With this design, a voltage generate circuit that constitutes a part of the head voltage generation circuit disposed in each print head also has versatility.
Therefore, when it is desired to differently control a voltage for each color, means for externally supplying ink color information, and the like to the voltage control circuit is necessary. Without this means, it is impossible the control the voltage for each ink color.
That is, when it is desired to differently control the voltage for each ink, it is necessary to separately supply ink color information to the voltage control circuit in each print head.
According to the arrangement as shown in the prior art 3, it is impossible to execute simultaneous print by the plurality of print heads, and further it is also impossible to execute recording at a high speed while the number of the control signal lines and the power supply lines in the cable can be reduced.
The prior art 4 describes nothing as to the number of the power supply lines when a plurality of print heads are employed. When it is desired to set a desired drive voltage to each print head, an infinite number of power supply lines must be prepared to supply a different voltage, which means an increase in the number of the power supply lines.
An object of the present invention, which was made in view of the above problems, is to provide an inkjet printer capable of reducing the number of cables of a carriage with a plurality of print heads, maintaining the versatility of the print heads, and recording an image having desired high quality while realizing simultaneous printing executed by the print heads.
More specifically, an object of the present invention is to reduce the number of power supply lines, and the like that constitute a cable by disposing a voltage generating unit, which generates a head drive voltage according to each of a plurality of inkjet heads from a voltage supplied from a main power supply, on a carriage side. Another object of the present invention is to realize simultaneous printing executed by a plurality of print heads, and is to control the voltages of each ink colors by permitting the voltage generation unit to optionally set a drive voltage to each inkjet head and to optionally convert the set voltage regardless of a voltage supplied from the main power supply. Still another object of the present invention is to print an image having desired high quality to which temperature information is added by providing a head temperature detector with each inkjet head.
To achieve the above objects, according to a first aspect of the present invention, there is provided a printer comprising: a carriage having a plurality of print heads mounted thereon and reciprocating with respect to a recording sheet; a main power supply disposed on a printer main body side; and a cable which establishes electric conduction between the main power supply and the plurality of print heads, wherein a voltage generating unit, which generates head drive voltages according to the plurality of print heads from the voltage supplied from the main power supply, is disposed on the carriage.
According to a second aspect of the present invention, there is provided a printer comprising: a printer main body; a carriage moving relatively to a recording medium; a power supply/communication cable which connects the printer main body to the carriage, wherein the printer main body comprises a main power supply and a master CPU; the carriage comprises a plurality of print heads and a voltage generating unit which generates head drive voltages according to the plurality of print heads; and the power supply/communication cable supplies a predetermined command from the master CPU and a voltage from the main power supply to the voltage generating unit.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.